How to add the chat component to the main Vue.js application and configure it to use the Firebase Firestore database.

To add the chat component to the main Vue.js application, you will need to import the component in your main.js file or where you have defined your Vue instance and register it as a global component or a local component to a specific parent component.

Here is an example of how you can register the chat component as a global component:

import Chat from './components/Chat.vue'
Vue.component('chat', Chat)

You can also register it as a local component to a specific parent component:

import Chat from './components/Chat.vue'
export default {
  components: { Chat },
  // other options
}

To use the Firebase Firestore database, you need to configure it in your Vue.js application by adding the following code to your main.js or where you have defined your Vue instance:

import firebase from 'firebase/app'
import 'firebase/firestore'

firebase.initializeApp({
  // Your firebase configuration goes here
})

const db = firebase.firestore()

You can also add this to your vuex store so that it can be used by all the components if you have one.

Then, you need to bind the messages data property to the Firebase Firestore database by adding the following code to your Vue.js application’s created() lifecycle method:

created() {
  this.bindFirestoreRef('messages', db.collection('messages'))
}

By following these steps, your main Vue.js application should now be configured to use the Firebase Firestore database and the chat component should be able to display, send and receive messages in real-time using Firebase Firestore.

Please note that this is just a high-level overview of the process and you may need to further customize and adjust your code to fit your specific needs.